JP2801284B2 - Electrophotographic copier - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates generally to electrophotographic copiers, and more particularly to cross-track and in-track platen alignment edges of copiers equipped with digital scanning devices. For calibration.

2. Description of the Related Art An electrophotographic copying machine, machine or instrument that stores digital signals of an original document in a storage device has a scanning device for digitizing a document image. Significant random access memory is required to store the entire page of digital data, and in some applications several pages of a multi-page original document must be stored. Because of the need for these large storage devices, it is desirable to store only the data needed to reproduce or duplicate the original document in the storage device.

Storage requirements, according to the prior art, were kept to a minimum by storing only the scanned area occupied by document pages. However, this requires precise positioning of the document pages in the scanning device.
Most scanning devices have a transparent platen on which documents are manually or automatically placed for scanning. Alignment marks, lines, or guides are placed on the platen, allowing the document to be positioned in the scanned platen area. By keeping the document properly aligned on the platen, and by scanning only the area within the alignment mark, the extra data is barred from taking up valuable storage space.

The difficulty with such alignment marks is that the scanning system accurately locates these marks on the platen to preserve memory and to accurately reproduce the original document properly centered on the copy paper. What you need to know. When the location is determined, changes in platen position, scan head alignment, illumination source orientation, etc., may change the location seen by the scanning device. Often, these devices are moved or changed during a service routine and require recalibration.

SUMMARY OF THE INVENTION It is therefore desirable to provide a system for easily determining the location of alignment marks or guides on a platen of a copying and duplicating apparatus, and it is an object of the present invention. Another object of the present invention is to require location processing only once if the relative positions of the marks do not change, and have been determined to avoid storing data that does not represent the original document in storage. Is to use the location.

EXAMPLES Throughout the following description, the same reference numerals indicate similar elements or members in all of the drawings.

Referring now to the drawings, and in particular to FIG. 1, there is illustrated the main components of a copying machine utilized in the alignment location process described in the present invention. Platen 10 is a transparent, flat member located on a copying machine for placing an original document thereon. Alignment marks, lines, or guides are located at two of the corners of platen 10 as indicated by marks 12 and 14. The pages of the document to be duplicated or copied are positioned against or aligned with the alignment marks 12 and 14 at the upper right corner 16 of the platen.

An apparatus for scanning an original document located on a platen is illustrated in FIG. 1, which illustrates a preferred embodiment of the present invention. In this embodiment, illumination source 18 directs a narrow beam of light down platen 10. The light beam, indicated by line 20, illuminates a line portion of the document being scanned. Light reflected from the scanned document is transmitted through a lens 22 to a sensing device 24, which can be a charge-coupled device (CCD). Linear CCD
24 can measure the intensity or density of light reflected from the entire line of the document scan. The number of pixels contained in the CCD 24 determine the resolution of the image content contained within the scanned line. A CCD suitable for use in a high resolution copier may have a pixel count of 5000.

In order to scan one page across, the illumination source 18 must be moved across the platen 10 so that the illuminated lines 20 and consequently the optically focused lines on the CCD 24 are copied or Move across the width of the page being duplicated.
This embodiment occurs with the scanning lens and the CCD 24 stationary and the illumination source 18 moved, but moving the platen on which the document is placed, or using a more complete light source and the CCD 2
Other arrangements, such as moving 4 relative to platen 10, can be used to scan the document area. Regardless of the configuration used, the result is essentially the same: the original document is scanned one line at a time, each line being a multiple that resolves the contents of each line down to a finer and smaller area. Of pixels. Once the signal from the CCD 24 is obtained, the data is sent to a control and processor system 26, which controls the data for later use and for use by a printer 28 as is well known in the art. Operate appropriately and store it.

FIG. 2 is a detailed view of the platen and associated electronic and optical supports required to carry out the present invention. The transparent platen 10 has the marks 12 and 14 shown in FIG.
And an in-track calibration line 12 and a cross-track calibration line 14. In some cases, lines 12 and 14 can be used for additional purposes, such as calibrating the response of the light and CCD systems for a matched response over the entire platen area. In each case, lines 12 and 14 are used to align the original document pages on the platen so that the original document pages are scanned properly and in the correct position.

In some devices, lines 12 and 14 may actually be thick strips of material attached to the platen surface, so that the original document page is pressed against corners 16 of the material strip and placed on platen 10 of the document. Can help with matching. Whatever the structure and composition of the lines 12 and 14, the effect is to give the platen 10 a constant surface with different colors to produce different density reflections as the scanning device passes under these platen matching regions. is there. The different densities reflected by the lines assist and enable the location of these lines relative to the physical location of the platen 10. Terms such as lines, marks, and guidance should be considered synonyms here.

Charge coupled device (CCD) 24 receives light from scan line 30 for illumination of the platen region by an illumination source not shown in FIG. For ease of illustration, scanning of the platen area
Assume that this is done by moving the CCD 24 in a direction 32 across the platen 10, thereby moving the scan line 30 across the alignment lines 12 and 14 and the platen surface. It should be noted that the actual method used to scan the platen area can be different from the method used in the illustration of FIG. 2 and can include using a fixed CCD and a moving illumination source. But it is emphasized.

Calibration of the alignment line is required as the platen moves relative to the other optical and mechanical components of the scanning system. During the calibration process, the platen is left blank, ie, document pages are not placed on the platen near alignment lines 12 and 14. Also, the platen cover remains open. In such a state, the area of the platen that is not covered by matching lines 12 and 14 is a dark high density area and CC
Not recognized as such by D24. However,
Lines 12 and 14, which are light-colored material, exhibit a low density, or light-colored area, as detected by CCD 24, at least below that exposed to CCD 24. It is the contrast or difference between the density areas of lines 12 and 14 and the other platen areas, which is used to determine the edges of the alignment lines, where the original document pages are aligned.

During the calibration process, in this embodiment, the CCD 24 moves in the direction 32 to move the scan line 30 across the platen area. CCD24
Is performed by a motor 34 and a gear mechanism 36 coupled to the CCD 24 as shown by line 38. Encoder 40, which can be a device of the type for counting the number of revolutions of a motor
Is arranged to send an encoder or rotation pulse to the microprocessor controller 42. Therefore, the control device 42
Can know the exact mechanical position of the CCD 24 as the line 30 scans across the platen area.

A fixed reference point is provided by a sensor 44, which may be an optical or mechanical sensor that detects the movement of the CCD 24 as it begins its scanning movement across the platen 10. During operation of the calibration process, motor 34 begins to move CCD 24 in the direction 32 from the position shown in FIG. CCD24 sensor 44
Is activated, the reference point for future use is stored in the non-volatile storage device 46 by the microprocessor controller 42. The data line is then scanned by the CCD 24 and the A / D
Sent to converter 48. While the scanning operation is taking place, encoder 40 provides data to microprocessor controller 42,
Thereby, the location of information from individual line scans can be determined for a given sensor 44 location.

As the scan line 30 moves in the direction 32 across the platen area, it first receives light reflected from the bottom of the alignment line 14 from the platen area. Due to the light-colored surface of the line 14, this reflected light has a low density and is suitably stored in the buffer 50. The "density" of light indicates the nature of light from image areas of known density. High density light comes from dark toner or black areas. Low density light comes from white areas. In this description, “density” is different from “intensity” indicating the amount of reflected light. As the scan continues, a point is reached where scan line 30 is on the left edge of alignment line 14 specifying the location where the location is to be determined. At this transition, the density of light reflected back to the CCD 24 is greatly increased due to the relatively black or dark image provided by the open platen 10 with the cover open. This data is stored in buffer 50 and additional data for a small distance past the edge of line 14 is stored in buffer 50 so that the line edge can be accurately located within a predetermined tolerance of possible line edge locations. Sufficient data is obtained for location. In addition to scanning for the edge of line 14, scanning for the edge of line 12 occurs during the same scanning operation. Since the line 30 partially overlaps the line 12, the pixels of the CCD corresponding to the area occupied by the lightly colored line 12 receive the low density light signal and open platen below the edge of the line 12. Pixels corresponding to the region receive the high density data signal. The signal is also taken over the sample area and stored in storage buffer 50. When the initial processing of scanning the empty platen occurs after a service routine or after other events that may change the location of the matching edge to a certain location, the data is then processed and a certain reference point is used. The location of the matching edge equal to the encoder pulse from is stored in non-volatile storage 46 for use during normal scanning operations.

FIG. 3 is an enlarged partial view of the upper right corner of the platen shown in FIG. According to FIG. 3, the alignment lines 12 and 14 are shown to intersect each other at the portion 54 and extend at right angles along the platen edges 56 and 58. The area inside the enclosure 60 is used to determine the location of the in-track alignment edge 15. Even though the scan of the line traveling across the platen 10 during the calibration process stores data for an area larger than the area bounded by the enclosure 60, the data is used to determine where the edge of the line 14 is located. The process of analyzing and processing the data need only examine the data in the enclosure 60. Enclosure 60 is platen and CCD
Is large enough that the portion within the enclosure 60 is always large enough to encompass the location of the edge 15 of the line 14, regardless of the mismatch. A similar theory applies to the enclosure 62 surrounding data that needs to be processed to locate the cross-track alignment edge 13 of the line 12. The thickness of lines 12 and 14 is not critical to the operation of the present invention. Thicknesses greater than the minimum identifiable thickness may be utilized. A thickness of 1.58 mm (1/16 inch) is considered sufficient.

FIG. 4 is a graph showing the operation of the threshold device 49 shown in FIG. The multi-bit digital voltage applied to the threshold device is represented by curve 64. When CCD is watching a low concentration region, the voltage of the curve 64 has a relatively high value V _1. As the transition edge is approached, the voltage on curve 64 begins to decrease and ultimately V ₂
To obtain the low level indicated by. The threshold level, shown by line 66, determines when the reduction in signal voltage changes the output from a single bit binary high to binary low. In the example shown in FIG. 4, this transition occurs at location 68 and is represented schematically by curve 70.

FIG. 5 is a flowchart of the software algorithm used to determine the location of the matching edge during the calibration process. According to FIG. 5, the process starts without placing the document on the platen. Block 72 represents the start and blocks 74 and 76 indicate the activation of the scanner movement and the detection of a low to high density transition during a line scan. When this transition occurs, the location where it occurs is stored in storage according to block 78. Thus, the location of the in-track alignment edge 15 shown in FIG. 3 is recorded in non-volatile storage for subsequent use by the device. block
Reference numerals 80, 82, and 84 denote algorithm operations for detecting a transition from low density to high density at a line scan pixel. When determined, the location of the cross-track alignment edge 13 shown in FIG. 3 is stored in non-volatile storage for future use. The flowchart illustrated in FIG. 5 is one of several that can be used to determine the location where the transition occurs from low to high density from stored data obtained during the initial scanning process. Is emphasized. Other algorithms that achieve substantially the same result can be used and will be apparent to those skilled in the art of writing computer software.

FIG. 6 is a flow chart of an algorithm that may be used to scan a document page after the calibration process has stored the location of the matching edge in storage. By using the algorithm of FIG. 6, marginless and extra stored data can be avoided and the orientation of the original document displayed in the reproduced copy is exactly matched. Blocks 86, 88 and
According to 90, the scanning device motion is activated or initiated, and when the position of the scanning device is correctly located at the previously stored location for the location of the alignment edge, the data on the document to be replicated is block 92. Are scanned and stored in the storage device. When scanning is complete, that is, when a complete page has been scanned, digitized, and stored in storage, the scanning process is completed as indicated by blocks 94 and 96. Normally, scanning is considered to be complete when the movement of the scanning device is sufficient to encompass the full size of the paper being replicated.

A novel and unique system for easily and quickly determining the location of a registration edge on a platen of a reproduction apparatus has been disclosed herein. The calibration process typically occurs when a previously stored location value is no longer accurate, such as after equipment maintenance. Since no additional hardware and / or alignment tools are needed to perform this calibration process, its use is very important to keep the xerographic reproduction and reproduction machine in a calibration and adjustment state with which to make accurate copies. Useful for

It is emphasized that many modifications can be made to the above-described devices without departing from the teachings of the present invention. All that is included in the above description or shown in the accompanying drawings should be interpreted as illustrative rather than limiting.

Further benefits and uses of the present invention will become more apparent upon consideration of the above detailed description and drawings.

[Brief description of the drawings]

FIG. 1 is a schematic view of the components of a copying machine required to calibrate a platen alignment edge, FIG. 2 is a detailed view of a platen and associated electronic and optical supports, and FIG. FIG. 4 is an enlarged partial view of the platen shown in FIG. 2, FIG. 4 is a graph illustrating the operation of the threshold device shown in FIG. 2, and FIG. 5 is an algorithm used to perform the calibration process. FIG. 6 is a flow chart, and FIG. 6 is a flow chart of an algorithm used to scan a document with data obtained when the algorithm shown in FIG. 5 is executed. 10 ... Platen, 12, 14 ... Alignment mark, 24 ... Detection device, 26 ... Control and processor system, 42 ... Control device, 44 ... Sensor, 46 ... Storage device, 48 ... A / D Transducer, 49 Threshold device, 66 Threshold.

Continuation of the front page (72) Inventor Lawrence B. Television, Parkside Lane, Rochester, New York, 14612, USA 14 (56) References JP-A-1-300670 (JP, A) .Cl. ⁶ , DB name) H04N 1/04-1/207

Claims (1)

(57) [Claims] An electrophotographic copier having a scanning system for converting image content of an original document into a digitized signal, said scanning system being a platen (10) on which the original document can be placed. A platen having the alignment guides (12, 14) thereon; means (24) for scanning the platen (10) to detect a change in image information density from the platen area; Means for processing the change in density to determine the position on the platen of (12,14) and storing the location of the alignment guide (12,14) relative to a fixed location (44) for subsequent retrieval Means (4
6) and means (42) to start storing digitized document signals immediately after the scanning system focuses on the area of the platen within the stored location of the alignment guides (12, 14). Electrophotographic copier.